Process for modifying polymers

ABSTRACT

A process for modifying polymers containing carboxyl, hydroxyl and/or phenolic hydroxyl groups. In the process, the polymers are reacted with a delta 2  mono- or bis-oxazoline, each substituted in the 2-position by an optionally substituted alkyl or alkenyl group containing from 7 to 23 carbon atoms. The modified polymers show reduced melt viscosities, lower adhesion and better slip characteristics than unmodified polymers.

FIELD OF THE INVENTION

This invention relates to a process for modifying polymers containingfunctional groups by reaction with delta² -oxazolines.

RELATED ART

It is known from the literature that delta² -oxazolines are capable ofreacting with various chemical compounds in a ring-opening reaction.Thus, ester amides of aminoethanol are formed, for example, from delta²-oxazolines substituted in the 2-position by reaction with carboxylicacids. Phenyl ethers derived from ethanol-amides are formed by reactionwith phenols while amino-amides or, optionally, amides are formed byreaction with amines. Further information on this subject can be foundin synoptic articles, cf. for example J. A. Frump, Chem. Rev. 71,483-505 (1971), more particularly pages 494-498, and H. Hellmann et al.,Angew. Chem. 78, 913-27 (1966).

The reaction of oxazolines with compounds containing carboxyl, aminoand/or phenolic hydroxyl groups has already been used to modifypolymers. Thus, U.S. Pat. No. 4,351,936 describes the reaction ofcarboxyl-terminated polyesters with oxazolines substituted in the2-position by amino groups, aminocarbonyl groups or ether groups. Thenumber of free carboxyl groups in the polyester molecules is reduced bythe reaction. GB 1,426,409 describes the reaction of phenylenebis-oxazolines with carboxyl-terminated polyesters which, besidesreducing the number of free carboxyl groups, also leads to an increasein molecular weight. Disadvantages of these processes include the poorreactivity of the phenylene bis-oxazolines and the monofunctionality ofthe alkylamino, alkylcarbamoyl and alkoxyoxazolines which prevents thedesired reduction in the molecular weight of the polyester duringprocessing.

BRIEF SUMMARY OF THE INVENTION

It has now been found that certain, preferably long-chain substituteddelta² -oxazolines and/or bis-delta² -oxazolines are far more suitablefor modifying polymers containing reactive functional groups.

The present invention relates to a process for modifying polymerscontaining carboxyl, amino and/or phenolic hydroxyl groups by reactionwith delta² -oxazolines, characterized in that 2-phenyloxazoline ormono- or bis-oxazolines substituted in the 2-position by a long-chain,optionally substituted alkyl or alkenyl radical containing 7 to 23carbon atoms in a linear chain are used as the delta² -oxazolines. Theprocess according to the invention is preferably used for modifyingpolyesters containing carboxyl groups.

The process according to the invention is distinguished from knownprocesses by the far higher reactivity of the delta² -oxazolines used.At the same time, the hydrolysis stability of polycondensates, such aspolyesters and polyamides, is distinctly improved where the long-chaincompounds preferably used are incorporated in the polymer molecule.Another advantage is that the delta² -oxazolines used show lowvolatility and, accordingly, can be reacted with the polymers at thehigh processing temperatures required without any need for furtherauxiliary measures. The polymers modified by the process according tothe invention show reduced melt viscosities and, in every case, loweradhesion and better slip behavior than the unmodified polymers.

DETAILED DESCRIPTION OF THE INVENTION

The process according to the invention is suitable for polymers varyingwidely in structure providing they contain carboxyl, amino and/orphenolic hydroxyl groups. The process is of particular interest forpolymers in which these substituents occur as terminal groups, moreparticularly for polyesters and polyamides, but also for polycarbonates.Examples of polymers such as these are, in particular, polyethyleneterephthalate, polybutylene terephthalate, polyamide 6, polyamide 6,6,polyamide 9, polyamide 11 and polyamide 12 and also the aromaticpolyamides, for example the types synthesized from aromatic diamines andaromatic dicarboxylic acids commercially available as Kevlar® andNomex®. If pure bis-oxazolines or mixtures of mono- and bis-oxazolinesare used for modifying these compounds, not only are the terminal groupsmodified, an increase in molecular weight is also obtained which, inmany cases, is highly desirable because often only low molecular weightsare obtained by the polycondensation reaction alone or, alternatively,the polycondensates are depolymerized during processing. Accordingly,the reaction is also of interest for recycling plastic waste consistingof various polycondensation products. In addition to the increase inmolecular weight, incompatible polymers are compatibilized by thelinkage and can thus be processed to form a polymer blend.

However, compounds in which carboxyl groups, amino groups and/orphenolic hydroxyl groups occur as lateral substituents may also be usedas the polymers. Examples of such compounds are polymers and copolymersof acrylic, methacrylic or maleic acid. These polymers can be completelyor partly modified by the process according to the invention, thehydrophilic or hydrophobic character of the polymer being adjustablewithin wide limits depending on the type and quantity of long-chaindelta² -oxazoline used. Polymers thus modified may be used, for example,as oil additives, as plastic additives or as polymer surfactants.

The delta² -oxazolines used in accordance with the invention areprimarily oxazolines substituted in the 2-position by the alkyl group ofa fatty acid containing a total of 8 to 24 carbon atoms or by the phenylgroup. Oxazolines such as these can be obtained in various ways,although the processes described in DE 38 24 982, DE 39 14 133 and DE 3914 159, which start out from carboxylic acids or carboxylic acid esters,have proved to be particularly useful. Accordingly, the disclosure ofthese patent applications is hereby included in this regard as part ofthe disclosure of the present application. In individual cases,oxazolines containing relatively long alkyl chains up to about C₄₀ mayof course also be used. According to DE 39 15 874, delta² -oxazolines ofwhich the alkyl group derives from a hydroxycarboxylic acid and,accordingly, contains a hydroxyl group can be reacted with diisocyanatesor polyisocyanates to form bis- or polyoxazolines in which the oxazolinerings are linked by urethane groups. Bis-oxazolines such as these areparticularly suitable for the purposes of the process according to theinvention. Similar bis-oxazolines which are also suitable are describedin hitherto unpublished patent application DE P 41 04 709.3. Thebis-oxazolines which can be obtained from the long-chainhydroxyfunctional delta² -oxazolines mentioned above bytransesterification with dicarboxylic acid esters and which aredescribed in hitherto unpublished patent application DE P 41 40 333.9are also suitable for the process according to the invention.Accordingly, the disclosure of the above-cited applications in regard tothe bis-oxazolines is hereby specifically included as part of thedisclosure of the present application.

Particular advantages are obtained in the modification of polymers, moreparticularly polyesters, with monofunctional delta² -oxazolines whichbear the alkyl/alkenyl group of ricinoleic acid, oleic acid or thesoybean oil fatty acid mixture in the 2-position. Where these oxazolinesare used, completely colorless and transparent products can be obtained,for example, from polyethylene terephthalate.

The conditions under which the process according to the invention can becarried out may be varied within very wide limits. Thus, the reactantsmay be reacted in solution or in suspension in suitable solvents orsuspending media. However, the possibility of carrying out the reactionin bulk without solvents or suspending media is generally of greateradvantage. Reaction temperatures above 100° C. are normally applied, thecatalysts typically used for the reaction between oxazoline andcarboxylic acids, phenols or amines, as known from the literature,optionally being added for acceleration. Where the reaction is carriedout in the absence of a solvent, reaction temperatures in the range fromabout 150° C. to around 320° C. are preferably applied, reactiontemperatures in the range from about 200° C. to about 280° C. beingparticularly preferred. Under these conditions, reaction times of 2 to10 minutes and preferably 3 to 5 minutes are often sufficient. Thereaction conditions and hence the necessary reaction times are of coursehighly dependent on the reactivity of the reactants and on theparticular conversion required. For the modification of terminal groupsin the polymers, 0.1 to 5 parts by weight of oxazoline are normally usedto 100 parts by weight of the polymer. This ratio does of course dependto a large extent upon the molecular weights of the reactants and, inindividual cases, may even be below or above these values. In ordercompletely to react all functional groups in the polymer, 1 to 2.5 molesand, more particularly, 1.2 to 2 moles of oxazoline groups are normallyused per mole of functional group. At all events, the high reactivity ofthe phenyl oxazoline and the long-chain substituted delta² -oxazolineshas an advantageous effect. Typical stirred reactors are suitable forcarrying out the reaction in solution or suspension. Screw extruders andsimilar machines suitable for mixing viscous melts are preferably usedwhere the reaction is carried out in bulk.

EXAMPLES Examples 1 to 5

In a DSK 42/7 twin-screw extruder (Brabender OHG, Duisburg), which wasequipped with a strip die and which had a screw diameter of 41.8 mm anda screw length of seven times that diameter (7D), 100 parts ofcarboxyl-terminated polyethylene terephthalate (48 equivalents COOH/10⁶g) were reacted with the quantities in parts of delta² -oxazoline shownin Table 1 at a temperature of 280° C. adjusted in all three heatingzones and at a screw speed of 25 r.p.m. The starting materials wereintroduced in the form of an intimate mixture of polyester granules andliquid oxazoline. The residence time in the extruder was around 6minutes. As can be seen from Table 1, the carboxyl content of thepolymer was considerably reduced.

                  TABLE 1                                                         ______________________________________                                                                         COOH content                                 Example                                                                              Delta.sup.2 -oxazoline                                                                           Parts  [eq/10.sup.6 g]                              ______________________________________                                        1      2-Heptadecenyloxazoline                                                                          1.0    5                                            2      2-Undecyloxazoline 0.7    7                                            3      2-Pentadecyloxazoline                                                                            1.2    5                                            4      2-Heptadecenyloxazoline                                                                          1.4    4                                            5      2-Phenyloxazoline  1.0    13                                           6      3-Soyaalkyloxazoline                                                                             2.0    6                                            7      2-(11-Hydroxyheptadec-8-                                                                         1.7    6                                                   enyl)-oxazoline (= ricinol-                                                   oxazoline)                                                             8      Bis-oxazoline of ricinol-                                                                        2.4    9                                                   oxazoline and 4,4'-diphenyl-                                                  methane diisocyanate                                                          (according to DE 39 15 874)                                            9      Bis-oxazoline of ricinol-                                                                        2.3    10                                                  oxazoline and tetramethyl-                                                    p-xylene diisocyanate                                                         (according to DE 39 15 874)                                            10     No addition        0.0    49                                           ______________________________________                                    

Examples 6 to 8

In the same twin-screw extruder as in Example 1, 100 parts of apolybutylene terephthalate ([η]³⁵° C._(o--ClC) ₆ H₄ OH=0.7 dl/g; 64equivalents COOH per 10⁶ g) were reacted with the quantities in parts ofbis-[2-(12-hydroxyheptadec-9-enyl)-oxazoline]-terephthalate (accordingto DE P 41 40 333.9) shown in Table 2. The temperature in all threeheating zones of the extruder was 250° C. and the screw speed 30 r.p.m.As can be seen from Table 2, the molecular weight (intrinsic viscosityη) was increased and, at the same time, the percentage content ofcarboxyl functions was reduced.

                  TABLE 2                                                         ______________________________________                                                Parts of    COOH content                                                                                ##STR1##                                    Example bisoxazoline                                                                              [eq./10.sup.6 g]                                                                           [dl/g]                                       ______________________________________                                        6       0.5         26           1.4                                          7       1.0         34           1.0                                          8       0.0         68           0.67                                         ______________________________________                                    

We claim:
 1. A process for modifying a polymer containing at least onefunctional group selected from the group consisting of carboxyl groups,amino groups and phenolic hydroxyl groups which comprises: reacting atleast one delta² -oxazoline selected from the group consisting ofmono-oxazolines substituted in the 2-position by an optionallysubstituted alkyl or alkenyl group containing 7 to 23 carbon atoms andbis-oxazolines substituted in the 2-position by an optionallysubstituted alkyl or alkenyl group containing 7 to 23 carbon atoms withthe polymer.
 2. The process as claimed in claim 1, wherein the polymercomprises plastic waste and the delta² -oxazoline is a bis-oxazoline. 3.The process as claimed in claim 1 wherein the polymer comprises apolyester.
 4. The process as claimed in claim 1 wherein the polymercomprises a polyamide.
 5. The process as claimed in claim 1 wherein thepolymer comprises an aromatic polyamide.
 6. The process as claimed inclaim 3, wherein the delta² -oxazoline comprises at least onemono-oxazoline bearing a group selected from the group consisting ofricinoleic acid alkyl group, oleic acid alkenyl group and alkyl andalkenyl groups from soybean oil fatty acid in the 2-position.
 7. Theprocess of claim 2 wherein the polymer comprises a polyester.
 8. Theprocess of claim 7 wherein polyester comprises at least one polyesterselected from the group consisting of polyethylene terephthalate andpolybutylene terephthalate.
 9. The process of claim 3 wherein thepolyester comprises at least one polyester selected from the groupconsisting of polyethylene terephthalate and polybutylene terephthalate.10. The process of claim 2 wherein the polymer comprises a polyamide.11. The process of claim 10 wherein the polyamide comprises at least onepolyamide selected from the group consisting of polyamide 6 andpolyamide 6,6.
 12. The process of claim 4 wherein the polyamidecomprises at least one polyamide selected from the group consistingpolyamide 6 and polyamide 6,6.
 13. The process of claim 4 wherein thepolyamide is formed from aromatic diamines and aromatic dicarboxylicacids.
 14. The process of claim 10 wherein the polyamide is formed fromaromatic diamines and aromatic dicarboxylic acids.
 15. The process ofclaim 7 wherein the delta² -oxazoline comprises at least onemono-oxazoline bearing a group selected from the group consisting ofricinoleic acid alkyl group, oleic acid aklenyl group and alkyl andalkenyl groups from soybean oil fatty acid in the 2-position.
 16. Theprocess of claim 8 wherein the delta² -oxazoline comprises at least onemono-oxazoline bearing a group selected from the group consisting ofricinoleic acid alkyl group, oleic acid akenyl group and allyl andalkenyl groups from soybean oil fatty acid in the 2-position.
 17. Theprocess of claim 9 wherein the delta² -oxazoline comprises at least onemono-oxazoline bearing a group selected from the group consisting ofricinoleic acid alkyl group, oleic acid akenyl group and alkyl andalkenyl groups from soybean oil fatty acid in the 2-position.
 18. Aprocess for modifying a polymer containing at least one functional groupselected from the group consisting of carboxy groups, amine groups, andphenolic hydroxy groups which comprises reacting at least one delta²-oxazoline selected from the group consisting of mono-oxazoline bearinga ricinoleic alkenyl group, mono-oxazoline bearing an oleic acid alkenylgroup, and soybean oil fatty acid alkyl and alkenyl groups in the2-position.
 19. The process of claim 18 wherein the polymer comprises apolyester.
 20. The process of claim 19 wherein the polyester comprisesat least one polyester selected from the group consisting ofpolyethylene terephthalate and polybutylene terephthalate.